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United States Patent | 5,055,743 |
Ekstrand | October 8, 1991 |
An improvement for a vacuum tube or a plasma tube comprises a cathode loop formed of a material suitable for induction heating. A support structure mounted inside the vacuum tube supports the cathode loop at a cathode position. A power supply mounted outside the vacuum tube includes an induction coil wrapped around the tube near the cathode position and generates an alternating electromagnetic field at the cathode position to induce heat in the cathode loop so that electrons are released into the vacuum tube. Finally, a DC bias is applied to the cathode through the support structure. The improved plasma tube with an induction heated cathode is particularly useful for an ion laser gain medium.
Inventors: | Ekstrand; John P. (Palo Alto, CA) |
Assignee: | Spectra Physics, Inc. (Mountain View, CA) |
Appl. No.: | 346469 |
Filed: | May 2, 1989 |
Current U.S. Class: | 315/111.51; 313/339; 313/356; 315/94; 315/111.21; 315/248 |
Intern'l Class: | H01J 007/24 |
Field of Search: | 315/94,105,248,111.51,111.21,111.41,111.81 313/337,339,356 |
2239642 | Apr., 1941 | Burkhardt et al. | 313/356. |
3509410 | Apr., 1970 | Banas et al. | 313/339. |
4339691 | Jul., 1982 | Moriniya et al. | 315/111. |
4812166 | Mar., 1989 | Saiki et al. | 315/111. |
4818916 | Apr., 1989 | Morrisroe | 315/111. |
4833294 | May., 1989 | Montaser et al. | 315/111. |